Add portable mode

If settings.ini is present next to the executable, will run in portable mode.
This results in settings, data, and cache all being in same folder as dupeGuru.

hscommon/desktop.py

@@ -30,7 +30,7 @@ def reveal_path(path):
     _reveal_path(str(path))
 
 
-def special_folder_path(special_folder, appname=None):
+def special_folder_path(special_folder, appname=None, portable=False):
     """Returns the path of ``special_folder``.
 
     ``special_folder`` is a SpecialFolder.* const. The result is the special folder for the current
@@ -38,7 +38,7 @@ def special_folder_path(special_folder, appname=None):
 
     You can override the application name with ``appname``. This argument is ingored under Qt.
     """
-    return _special_folder_path(special_folder, appname)
+    return _special_folder_path(special_folder, appname, portable=portable)
 
 
 try:
@@ -54,7 +54,7 @@ try:
     _open_path = proxy.openPath_
     _reveal_path = proxy.revealPath_
 
-    def _special_folder_path(special_folder, appname=None):
+    def _special_folder_path(special_folder, appname=None, portable=False):
         if special_folder == SpecialFolder.Cache:
             base = proxy.getCachePath()
         else:
@@ -68,6 +68,9 @@ except ImportError:
     try:
         from PyQt5.QtCore import QUrl, QStandardPaths
         from PyQt5.QtGui import QDesktopServices
+        from qtlib.util import getAppData
+        from core.util import executable_folder
+        from hscommon.plat import ISWINDOWS
 
         def _open_url(url):
             QDesktopServices.openUrl(QUrl(url))
@@ -79,12 +82,15 @@ except ImportError:
         def _reveal_path(path):
             _open_path(op.dirname(str(path)))
 
-        def _special_folder_path(special_folder, appname=None):
+        def _special_folder_path(special_folder, appname=None, portable=False):
             if special_folder == SpecialFolder.Cache:
-                qtfolder = QStandardPaths.CacheLocation
+                if ISWINDOWS and portable:
+                    folder = op.join(executable_folder(), "cache")
+                else:
+                    folder = QStandardPaths.standardLocations(QStandardPaths.CacheLocation)[0]
             else:
-                qtfolder = QStandardPaths.DataLocation
-            return QStandardPaths.standardLocations(qtfolder)[0]
+                folder = getAppData(portable)
+            return folder
 
     except ImportError:
         # We're either running tests, and these functions don't matter much or we're in a really
@@ -97,5 +103,5 @@ except ImportError:
         def _reveal_path(path):
             pass
 
-        def _special_folder_path(special_folder, appname=None):
+        def _special_folder_path(special_folder, appname=None, portable=False):
             return "/tmp"